β3肾上腺素能受体与心房颤动心房代谢重构关系研究

Atrial fibrillation (AF) is a progressive disease and is the most common sustained cardiac arrhythmia. The processes that lead to the worsening of AF over time include electrical, constructural, neurohormonal remodeling, and these may all associated with energetic metabolic remodeling. Cardiac metabolic remodelling is characterized by a spectrum of alterations in cardiac energy and substrate metabolism, thereby alterations in cardiac constructions and functions occur accordingly. Recently β3-adrenoceptor (β3-AR) is increasingly recognized as a major contributor to control of normal and pathological cardiac function. It is evidenced that β3-AR plays a central role in metabolic remodeling of HF. However, the functional role of β3-AR activation in AF is not known. The OBJECTIVE of this proposal is to elucidate the role of and mechanisms underlying β3-AR-mediated cAMP-PPARγ/PGC-1α signal pathway in AF. The overall hypothesis is that up-regulation of artial β3-ARs, is an important cause of AF. The proposed studies stem from our recent observations made in our established AF rabbit model that acute AF up-regulates β3-ARs producing atrial electrical remodeling and metabolic remodeling. Treatment with a β3-antagonist (ANT) reversed these effects. Although the underlying mechanisms remain to be determined, our preliminary findings suggest that altered β3-AR signaling system may be a critical element in the development of AF. Thus, agents that interfere with β3-ARs may offer novel benefits over existing therapies for AF. Studies will be conducted in normal control and two groups of AF rabbits with and without a β3-ANT treatment. Using an integrative and multidisciplinary approach with in-depth physiology and molecular analysis AF will be characterized at 3 levels (intact animals, cultured atria myocytes, and molecular) to define the role and mechanism of β3-ANT therapy in AF. This is a highly innovative proposal that focuses on a novel concept. The outcomes will have significant translational value and high impact, which will enhance our understanding of the pivotal mechanisms of AF and lead to new therapeutic targets for this important problem.

心房颤动（AF）具有自身进展性和自身延续性，与AF时心房发生结构、电、神经和功能重构相关，而上述重构的发生、维持及进展均与能量代谢重构密切相关。代谢重构时，心肌细胞主要供能物质代谢紊乱引起心脏能量代谢途径改变，从而导致一系列结构和功能异常。β3肾上腺素能受体与心脏功能密切相关，AF时，β3受体表达上调，引起心脏结构及功能改变。β3受体与心力衰竭能量代谢重构关系密切，但与AF代谢重构关系尚不清楚。申请者研究已证实，抑制β3受体可减轻AF电重构，并缓解AF能量缺乏。基于上述理论，本研究通过建立家兔快速心房起搏模型及房颤细胞膜型，并予β3受体激动剂及抑制剂干预，分别从整体动物、细胞及分子水平观察β3受体通过cAMP-PPARγ/PGC-1通路对AF代谢重构的影响及其机制。此研究结果有助于开拓AF心房重构研究新领域，为临床防治AF寻找新的药物治疗靶点提供重要基础理论和实验依据。

心房颤动（AF）具有自身进展性和自身延续性，与AF时心房发生结构、电和功能重构相关，而上述重构的发生、维持及进展均与能量代谢重构密切相关。β3-AR与心力衰竭能量代谢重构关系密切，在AF时亦表达上调，但与AF代谢重构关系尚不清楚。本研究利用成年家兔以及HL-1细胞系，随机分为空白对照组、起搏组、β3-AR激动剂组和β3-AR抑制剂组。检测各组家兔体表心电图，房颤诱发率及有效不应期（AERP）；同时，应用PAS染色检测各组心房肌糖原累积情况，油红o染色检测细胞内脂滴积聚程度。采用免疫印迹(western-blot)和实时定量PCR(real time RT-PCR)方法检测各组家兔心房肌β3-AR表达，以及葡萄糖转运关键酶葡萄糖转运子4（GLUT-4）脂肪酸转运关键调控因子CD36和脂肪酸代谢关键酶CPT-1基因水平及蛋白表达变化。同时检测代谢调控关键酶过氧化物酶体增殖物激活受体家族（PPARs）及其共激活物PGC-1ɑ的变化。使用试剂盒检测代谢过程中脂肪酸含量变化，应用高效液相色谱层析仪监测心房肌组织中ATP含量。研究结果显示快速心房起搏使β3-AR表达增高，给予β3-AR抑制剂后，可降低其表达。与对照组相比，起搏组AERP缩短（P < 0.01），ATP含量减少，心肌游离脂肪酸减少（P < 0.01），血浆游离脂肪酸浓度明显增多（P < 0.01），且PAS染色及油红o染色示心肌组织糖原积聚，细胞内脂滴减少，同时GLUT-4及CD36、CPT-1基因水平及蛋白表达下降，心肌组织底物利用改变，出现代谢重构。给予β3-AR激动剂后，ATP含量进一步下降( P < 0.05)，糖脂代谢紊乱，加剧能量代谢恶化，反之给予β3-AR抑制剂后，可减轻代谢重构。另外，起搏组与对照组相比，代谢调控因子PPAR-ɑ/PGC-1ɑ基因水平及蛋白水平均下降，激动β3-AR可进一步加剧PPAR-ɑ/PGC-1ɑ的下降，而抑制β3-AR后，则可恢复PPAR-ɑ/PGC-1ɑ表达，推测PPARs/PGC-1ɑ参与β3-AR介导的AF代谢重构。β3-AR调节有望成为治疗AF的新靶点。